Though the former did achieve democratic legitimacy
In what sense? For sure they brought the British government to the negotiating table and established the Free State. But they failed to repeal the Government of Ireland Act which established NI and in turn led to a century littered with political and sectarian violence in a basket case, church controlled, State.
The Provos too brought the British government to the negotiating table and, like GOIRA, failed to repeal the GoI Act. At best, the Provo campaign may have hopped one of those stepping stones (backwards or forwards) that Collins mentioned in his push for peace. A derisory return either way.
Ah yes Sunningdale, for slow learners, the quip associated with Séamus Mallon. Sunningdale collapsed at the hands of loyalists who brought the economy and society to a standstill. The irony being lost on Mallon that you cannot come to a political settlement for peace if the protagonists engaged in violence are excluded from the negotiation. It was a stance he would hold firm to for the rest of his political life only for Hume to undercut this position with his engagement with Adams. After which ceasefire would eventually emerge despite all the obstacles, obstructions and disdain he had to endure.
Slow learners indeed.
There is absolutely nothing in the Provo campaign that is worthy of commemorating
Obviously, depending on your perspective, this is a legitimate held view but from a SF perspective and the communities they represent they consider otherwise. Obviously they failed, like GOIRA and all others before them, to forceabley move Britain out of Ireland entirely. But they would hold the struggles of those who stood against internment, criminalisation, collusion, shoot-to-kill, in the face of a military might of the BA. The sacrifices of the Hunger Strikers - regardless of what you think of the individuals or their cause, the act of self-sacrifice resonated around the world smashing the policy of criminalisation.
From a military perspective, and this brings us back to Stanley, Warrenpoint was considered a huge success, similar to Kilmichael before it.
Striking at the heart of the political establishment, twice, in Brighton and in Downing St*
The British Army have I am sure in their time committed war crimes
I sense you are leaving room for doubt?
that there is some sort of equivalence between BA and the PIRA in terms of either honour or shame
In terms of shame there is little difference. They murdered innocents, children, the unborn. They cover-up their atrocities protecting the perpetrators from justice. They engaged in torture and they conspired to plant bombs indiscriminately.
In terms of honour, the only honour is for ourselves as a people to ensure it never descends into bloodshed again.
*
I don't proclaim these as events worth commemorating, rather from an objective military view they would be considered as a success. Similarly events like Loughgall and Gibraltar would be considered successes on the British side.